Latchable, polarization-agile reciprocal phase shifter

ABSTRACT

A latchable ferrite phase shifter useful in microwave phasescanned antenna arrays and having reciprocal phase-shift properties. An axial arrangement of selectably magnetizable magnetization means in cooperation with the latchable ferrite allows use of a single longitudinal ferrite rod and fewer magnetization elements, as to demonstrate lower insertion losses and lower manufacturing costs, as well as latchable reciprocal phase shift properties.

United States Patent Roberts et al.

[ 51 Oct. 10, 1972 [54] LATCHABLE, POLARIZATION-AGILE RECIPROCAL PHASE SHIFTER [72] Inventors: Roger G. Roberts, Placentia; Jerry A. Algeo, Buena Park, both of Calif.

[73] Assignee: North American Rockwell Corporation 221 Filed: April 22, 1971 [21] Appl. No.: 136,459

52 U.S.Cl ..333/31 A, 333/24.1,333/24.3 [51] met ..H01p 1/18 [58] Field of Search .333/1.1, 21 R, 21 A, 24.1-24.3,

ass/311mm [56] References Cited UNITED STATES PATENTS Fox ..33 3 31 3,100,287 8/1963 Scharfman et a1 ..333/24.l

Primary Examiner-Paul L. Gensler -AttomeyL. Lee Humphries, 1-1. Frederick Hamann and Rolf M. Pitts [5 7] ABSTRACT A latchable ferrite phase shifter useful in microwave phase-scanned antenna arrays and having reciprocal phase-shift properties. An axial arrangement of selectably magnetizable magnetization means in cooperation with the latchable ferrite allows use of a single longitudinal ferrite rod and fewer magnetization elements, as to demonstrate lower insertion losses and lower manufacturing costs, as well as latchable reciprocal phase shift properties.

9 Claims, 10 Drawing Figures PATENTED 10 I973- 3 698, 0.08

sum 1 or 4 l PRIOR ART FIG " INVENTORS JER A. ALGEO BY no a. ROBERTS ATTORNEY PATENTEDHN 10 m2 SHEEI 2 OF 4 1 L 2 11 L/.. 5 m a 2 w FIG. 3

INVENTORS RY A..AL6E0 ER 6. noaems I utt ATTORNEY FIG.6

INJECTED I RECEIVED ENERGY I ENERGY PATENTEBnm 10 I972 3.698.008

sum u or 4 a ENERGY T TRANSMIT TED EMERGENT ENERGY I INVENTORS JERRY A. ALGEO ROGER G. ROBERTS ATTORNEY BACKGROUND OF THE INVENTION In the art of electronically scanned radar antennas employing phased-arrays, a planar matrix of radiating elements is employed, the elements being excited by a common source of microwave energy. By selective insertion of electronically controlled discrete phase-shifts in the feeds of such radiating elements, the direction of the radiating wave front from such array may be directionally scanned or otherwise controlled. The direction to which such antenna responds in a receiving mode may be similarly controlled. Where, however, the phase-shifter is not a reciprocal device, as to provide a like phase-shift to received energy travelling in one direction therethrough as for transmitted energy propagated in the opposite direction therethrough, then it is necessary to reset the electronically controlled phase shifters of the array for the receive-mode to achieve a like set of phase shifts and corresponding direction of directivity as in the transmit mode.

The propogation constant of a guided electromagnetic wave in a ferrite magnetic medium can be controlled by the application of a biasing magnetic field. The phase-shifter prior art includes reciprocal, latching ferrite phase shifters, in which the phase shift is adjusted by adjusting the remnant magnetization of the ferrite by suitably pulsing a latching coil wound about a portion of the ferrite as described in U.S. Pat. No. 3,510,675. The insertion phase for a given ferrite phase-shifter structure will depend upon the guide geometry and the material parameters of the ferrite (such as the propagation constant, magnetic saturation limit, etc.). Practical ferrite phase shifters are operated under conditions of partial magnetization. For a plane wave propagating in a theoretically infinite ferrite medium along the direction of an applied field, the normal modes of propagation are right and left circularly polarized waves, each having a different propagation constant.

A linearly polarized wave propagating in such ferrite medium may be represented as the superposition of a right circularly polarized wave and left circularly polarized wave of equal amplitudes. Because such oppositely circularly polarized waves have different propagation constants, as noted above, they will propagate with different phase constants. As a result, the polarization plane of the linear polarization wave (represented by the two superimposed oppositely polarized waves) will experience a rotation as a function of propagation distance in the medium, which polarization rotation is referred to as a non-reciprocal Faraday rotation. Letting B- and B represent the propagation constants for the left and right circular polarizations, respectively, the angle of polarization rotation 0, as a function of distance I through the ferrite medium, is given as:

Polarization rotation, /(B l3,.)l l The phase shift d: associated with such propogation is given as:

Phase shift, d: k (B +B )l 2 while the combined phase rotation 111(1) is defined as:

Reciprocal ferrite phase shifters have many potential advantages for microwave inertialess scanning arrays. One advantage is the inherent ability to handle relatively high peak power and average power levels in a structure that is basically simple and capable of low cost volume production. Operation at remanent bias flux levels permits moderately fast switching with a latching memory feature. When such latching memory feature is combined with a metered flux electronic drive technique (such as that described in US. Pat. No. 3,510,675 a significant degree of temperature stability can be obtained in the phase shift characteriestics of the ferrite phase shifter. Also, the reciprocal nature of the phase shift allows transmitting and receiving functions to occur at a particular antenna beam orientation or direction without resetting the phase shifters of the array. Thus, it is not necessary to reset any array used in a radar application except when a change of beam direction or beam shape is desired.

The principal of operation of a reciprocal ferrite phase shifter involves the suppression of cancellation of the above-described Faraday rotation 0. One technique of Faraday rotation suppression is the use of a TEM- like structure the geometry of which is selected (relative to the desired operating frequency) such that a cross-polarized mode is normally cut-off, whereby propagation of circular polarization may not be supported therein. The suppression of the ability to support circular polarization thus tends to suppress the Faraday rotation associated with the equal-amplitude, oppositely circularly polarized components by which a linear polarization may be defined. Thus, reciprocal phase-shift of a preselected linear polarization results when the waveguide geometry is distorted so as to just suppress the Faraday rotation as in the Reggia-Spencer type phase shifter, or where the Faraday rotation effect is cancelled as in the bucking rotator type phase shifter.

The Reggia-Spencer device employs an axially magnetized ferrite rod adjacent and parallel to a rectangular waveguide and having a latching assembly with magnetizing winding wound about the waveguide. Reciprocal phase shift is obtained by non-reciprocal coupling of two waveguide modes, one a normally dominant TE -like mode and the other a normally cutoff cross-polarized mode. However, such devices tend to display lack of phase stability over wide ranges of temperature and RF average power. Further, because of the phase-sense as a function of frequency, such devices are limited to narrow band applications. Moreover, where the Faraday rotation is only imperfectly suppressed, severe impedance mismatch problems are apt to occur in terminal sections of the structure.

The bucking rotator phase shifter employs two identical cascaded or tandem-connected Faraday rotators oppositely magnetized, whereby non-reciprocal polarization rotation and associated phase shift effects are cancelled, while only a small reciprocal phase-shift is obtained (nominally about 4 percent of the total insertion phase shift). In other words, polarization-insensitive reciprocal phase-shift properties may be obtained for the bucking rotator type device by using large ampere-turns of magnetization, requiring high continuous operating power and limiting switching to slow switching speeds.

A further description of such prior art reciprocal phase shifters is described in an article Three New Ferrite Phase Shifters by H. Scharfman at page 1,456 of the Oct. 1956 Proceedings of the IRE. However, in general such prior art latching type phase-shift devices, in addition to the above-noted performance limitations, have been reciprocal in operation only for a preselected linear polarization and over a limited bandwidth percent).

Attempts to provide polarization-agile reciprocal devices have involved axially extended structures having (1 high insertion losses or a low figure of merit Al db in terms of attenuation (db suffered to effect a given maximum range of phase shift (A (2 associated high unit production costs, end (3 limited bandwidth performance.

In order to accommodate reciprocal phase shifting of all polarization senses by prior art devices, it has been necessary to resolve the incident excitation into two mutually orthogonal linearly polarized waves, applied (by means of a first orthogonal mode junction) to mutually exclusive ones of two discrete phase-shifter channels. The two channels are then switched in synchronism to provide identical insertion phases. A second orthogonal mode junction reconstructs the incident polarization from the emergent energy of the two phase-shifter channels. Such design approach suffers high insertion losses, imposes certain design constraints upon an antenna system employing it, and the synchronously switched dual channels thereof involve duplications of equipment and attendant increased production costs.

Yet a single channel alternate approach for polarization-agile, reciprocal phase-shifters employing latching ferrites has involved the use of plurality of discrete axially cascaded elements of ferrite and non-ferrite elements of like dielectric properties, involving high insertion losses, high manufacturing costs, and assemblies of increased bulk and weight.

SUMMARY OF THE INVENTION By means of the concept of the subject invention, the above noted shortcomings of the prior art are avoided and there is provided a reciprocal latching ferrite phase shifter assembly selectively responsive to preselected polarizations.

In a preferred embodiment of the invention there is provided a first and second passive non-reciprocal quarter wave plate at a respective first and second axial extremity of a latchable phase shifter. There is further provided polarization switching means interposed between the latchable phase shifter and the second quarter wave plate for providing a selected one of three preselected polarization phase rotation states: )t4 A4 and 0. A passive reciprocal quarter wave plate axially adjacent the second passive non-reciprocal quarter wave plate forms a second axial extremity of the phase shifter assembly, the first passive non-reciprocal quarter wave plate forming a first terminal of the assembly. Such assembly may be conveniently constructed of a single longitudinal ferrite core radially about which are disposed the magnetizing means comprising the non-reciprocal quarter wave plate, latching means and polarization rotation means and at an axial extremity of which is bonded a passive reciprocal quarter wave plate of like dielectric constant as the ferrite core.

In normal reciprocal operation of the abovedescribed arrangement, a preselected linear polarization of a preselected sense and applied to the first terminal of the assembly, is converted to circular polarization prior to transport through the latching means, which means imparts a selected phase shift. The switchable polarization phase rotation means cooperates (in a reference magnetization state) with the second non-reciprocal quarter wave plate to change the delayed circularly polarized wave to a linear polarization phase-rotated to 45 relative to the original injection plane of polarization. The passive reciprocal quarter wave plate cooperates with the delayed 45 rotated linear polarization wave to provide an emergent delayed circular polarization.

By adjusting the magnetization state of the switchable polarization from the reference state to provide one of a iM phase rotation, one of a horizontal and vertical polarization is imparted to the delayed wave, which linear polarization is unaffected by the cooperation of the passive second non-reciprocal quarter wave plate and the reciprocal quarter wave plate, whereby a delayed linear emergent polarization is provided.

Because of the reciprocal mode of cooperation of such arrangement, the receipt (in any one of such three modes of the three-state polarization switch) at the second terminal or port of a polarization similar to that transmitted therefrom will produce a linear polarization output at the first terminal or port similar to that applied thereto for transmission.

Because the above described arrangement can be constructed about a single integral ferrite core and employing fewer components, it is cheaper to produce and may be constructed of a shorter length as to reduce insertion losses. In other words, lower production costs, reduced bulk and weight and an improved performance (figure of merit) are obtained.

Accordingly, it is an object of the invention to provide an improved latchable phase shifter.

It is another object of the invention to provide a latchable phase shifter is both reciprocal and selectively responsive to pre-selected polarizations.

It is a further object to provide a latchable, reciprocal, phase-agile phase shifter which may be constructed about a single integral ferrite core.

Yet another object is to provide a latchable, reciprocal polarization-agile phase shifter which both has a high figure of merit and is more economical to produce.

Still another object is to provide a latchable reciprocal phase shifter having both improved performance and reduced bulk and weight.

These and other objects of the invention will become apparent from the following description, taken together with the accompanying drawings in which:

DESCRIPTION OF THE FIGURES FIG. 1 is an illustration in perspective of a reciprocal, latching ferrite phase shifter;

FIG. 2 is an illustration in perspective of a preferred embodiment of the invention;

FIGS. 3, 4, 5 and 6 are transverse central sections taken at various-longitudinal stations axially along the device of FIG. 2 and further illustrating certain components thereof;

FIG. 7 is an exploded view of the externally concentric core of the switchable quarter wave plate shown in FIGS. 2 and 4; and

FIGS. 8A, B and C are families of vector diagrams for successive longitudinal stations axially along the device of FIG. 2.

In the figures, like reference characters refer to like parts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is illustrated a prior art phase-agile reciprocal latchable phase shifter, comprising a longitudinal assembly of longitudinally magnetizable discrete ferrite elements and non-ferrite elements having a like dielectric constant as the ferrite elements. There are provided three passive nonreciprocal quarter wave plate elements 11a, 11b and 11c, each of a like ferrite of square cross-section and having axially oriented magnetization means a, 15b, 15c and 15d about the periphery thereof. Three passive reciprocal (non-ferrite) quarter wave plate elements 12a, 12b and 120 are also provided. Elements 12a and 12b are placed at either portof a latchable phaseshifter element 13, element 12a being interposed between elements 11a and 13 and element 12b being interposed between elements 12 and 11b. An axially magnetizable three-state polarization rotator 14 and reciprocal element 12c are axially interposed between non-reciprocal elements 11b and 11c. Also, reciprocal element 12c differs from elements 12a and 12b in that the dielectric slab or quarter wave delay element 12:: is rotated 45 about the longitudinal axis of the assembly.

In normal operation of the arrangement of FIG. 1, the introduction of a vertically linearly polarized microwave signal at the input port formed by nonreciprocal 45 polarization rotor element 11a suffers a 45 polarization rotation, which may be represented by horizontal and vertical polarization components of resolution. Reciprocal quarter plate 12a delays the horizontal component relative to the vertical component, thus producing a right handed circular polarization from the resolved linear polarization, for phase-shifting by the latchable phase-shifter 13.

The application of a selected current pulse to t he winding 16 of phase-shifter 13 will result in a remanent axial magnetization which is substantially preserved by the iron-keepers 17a, 17b, 17c and 17d externally arranged about winding 16, as to produce an associated phase-shift of a circularly polarized wave propagated therethrough. Second reciprocal element 12b delays the horizontal component of the circularly polarized wave an additional quarter wave length, whereby such delayed component is now shifted a half-wave length relative to the vertical component as to be coplanar with the reversed sense thereof. The resultant .rotated linear polarization wave is then rotated by second nonreciprocal 45 polarization rotor 11b to provide a linear polarization coplanar with that initially inserted (at element lla and selectively delayed (by the cooperation of element 13).

Elements 14, 12c and 110 cooperate to selectively provide a selected one of three polarization states for the selectively delayed emergent wave. Where a reference axial magnetization state is maintained in polarization switching means 14, then the vertical linear polarization input to element 14 from element 11b is translated through element 14 and converted to circular polarization in element 120 which is essentially unaffected by third passive non-reciprocal means 11c.

When, however, polarization means 14 is switched from the reference state to either of two other states, as to effect either a +45 or 45 polarization rotation, then reciprocal means 12c cannot cooperate therewith to produce a circular polarization and the 145 -rotated linear polarization is unaffected. Non-reciprocal 45 rotor then cooperates to monotonically rotate the linear polarization an additional 45 whereby either horizontal or vertical linear emergent polarization is provided, dependent upon the sense of the 45 rotation selectively imparted by the switched state of switching means 14.

The axially magnetized device magnetized device of FIG. 1, while thus adapted to 'switchably providing selected emergent polarizations of a selectively delayed microwave in response to an inserted vertical polarization, demonstrates certain inherent disadvantages. The large number of components required by such axial magnetization scheme involve high unit production costs and high insertion losses. Such high unit production costs are due, not only to the large number of components employed, but due to the fact that axial sections are alternately of ferrite and non-ferrite elements, requiring cutting and bonding. Also, care must be used in shaping such pieces and joining them to assure a proper axial alignment and rotational orientation.

The long length associated with such assembly, in providing attenuation or insertion losses, thus reduces the performance figure of merit (Ada or maximum phase shift (Ada obtainable with an associated insertion loss (db Moreover, such long length of the device increases the bulk and weight of antenna arrays employing such devices.

In a preferred embodiment of the subject invention, non-axial magnetization is employed in a highly efficient mechanization, whereby the above-noted shortcomings are avoided, as is apparent from FIG. 2.

Referring now to FIG. 2, there is illustrated a preferred embodiment of the invention. There is provided a single integral longitudinal ferrite rod of substantially square cross-section and having magnetization elements arranged thereabout and'therealong and further having a passive reciprocal (non-ferrite) quarter wave plate 12 bonded to an axial extremity thereof and comprising a block of dielectric material in which is sandwiched slab 112, shown more particularly in transverse vertical section in FIG. 6. At either axial extremity of ferrite rod 18 there are peripherally or externally concentrically arranged four magnetization means or permanent magnets which cooperate with an associated axial sector of rod 18 as a passive nonreciprocal quarter wave plate.

At a first extremity a first non-reciprocal quarter wave plate 111a is formed by the cooperation of permanent magnets 115a, 115b, 1150 and 115d, the magnetic polarizations of which are radially oriented, opposing magnets 115a and 1l5c (or 115b and 115d of pairs of opposing magnets being oppositely poled, and adjacent ones of the four magnets being mutually oppositely poled, as shown more clearly in the vertical section of FIG. 3. In other words, the two pairs of magnets are oppositely poled, and the two diametrically opposed magnets of each pair are oppositely poled.

At the second extremity of ferrite rod 18 a second passive non-reciprocal quarter wave plate lllb is formed by the cooperation of permanent magnets 215a, 215b, 2150 and 215d, the magnetic polarization of which are transversely oriented of the longitudinal axis of the device of FIG. 2, as is more clearly seen in FIG. 5. Opposing magnets 215a and 215a (or 21511 and 215d of pairs of opposing magnetics are oppositely poled, and adjacent ones of the four magnets are mutually oppositely poled. In other words, the two pairs of magnets are oppositely poled, and the two diametrically opposed magnets of each pair are oppositely poled.

A latching phase shifter 13 is formed by a latching winding 16 slipped upon or wound about ferrite rod 18 at an axial sector adjacent that of non-reciprocal quarter wave plate 111a, and the addition'of magnetic keepers 17, corresponding to the like elements of FIG. 1. There is further included in thearrangement of FIG. 2 polarization switching means or a switchable nonreciprocal quarter wave plate 19 axially intermediate latching means 13 and second passive non-reciprocal quarter wave plate 1 1 1b, and comprising a ferrite yoke 20 externally concentrically of rod 18 and four equiangularly spaced radially extending pole pieces 21a, 21b,

21c and 21d (connecting yoke 20 and ferrite core 18 in magnetic circuit). Electromagnetic windings upon the pole pieces are employedfor selectively oppositely magnetizing contiguous pole pieces.

The externally concentric yoke 20 with poles 21a, 21b, 21c and 21d (illustrated in FIG. 4) and forming switchable non-reciprocal quarter wave plate 19 (of FIG. 2), may be conveniently formed of quadrant sections 20a, 20b, 20c and 20d formed by severing the assembly along two mutually orthogonal planes of symmetry each of which includes the longitudinal axis of rod 18 and also bisects a mutually exclusive pair of diametrically opposed poles, as shown in the exploded view of FIG. 7. Y

In construction, the longitudinal surfaces of ferrite rod 18 and quarter wave plate 12 are metallized by electroplating with gold or the like, so as to better function as a waveguide, the longitudinal edges of rod 18 and dielectric 12 being chamfered slightly in order to enable a better electroplating bond. It is also deemed desirable to polish the surfaces-to-be-plated of the ceramic guide prior to plating or metallizing. Also, as shown in FIGS. 2, 3, 4 and 5, ferrite rod 18 may include a longitudinally extending aperture down the center thereof.

In normal operation of the arrangement of FIG. 2, a vertical linear polarization microwave input, applied to element 1 1 1a (as an input port of the device of FIG. 1) becomes circularly polarized by the cooperation of radially magnetized first non-reciprocal quarter wave plate 111a, similarly as the combined cooperation of elements 11a and 12a of FIG. 2. Such circularly polarized wave is then selectively phase-shifted or delayed by the remanent axial magnetization of latching phase shifter 13, the delayed circular polarization being transported through polarization switching further quarter wave phase delay a preselected component (e.g., horizontal) of circularly polarized wave resulting in a 45-rotated linear polarization. A

horizontal component of such rotated linear polarization is then quarter wave phase delayed relative to a vertical component thereof by element 12 as to provide an emergent or transmitted circular polarization.

By similarly analyzing (in FIG. 8A) the receipt of a like circularly polarized electromagnetic wave at the second or transmit/receive port (station 5) of the device of FIG. 2, it is seen that such device is clearly reciprocal, providing a vertically linearly polarized output at port 1 thereof (station 1).

In one of a second and third switched mode of polarization switching means 19, a +A/4 or )t/4 (positive or negative) quarter-wave length phase shift shifts the horizontal components of resolution of the polarization vectors, relative to the vertical components thereof.

means 19 (in a reference state), with the polarization The response of elements 1 11b and 12 to such selectively phase-shifted components of the polarization vectors results in a cancellation of either the vertical or horizontal component, as to provide a transmitted horizontal polarization for the +)t/4 switch mode (FIG. 8B) and a transmitted vertical polarization for the )./4 switch mode (FIG. 8C), both of which modes are fully reciprocal. In other words, in receiving energy at the transmit port (station 5) of like polarization as that transmitted from such port in a given switch mode of switch 19, an emergent vertical linear polarization is commonly produced at the other port (station 1).

Accordingly, there has been described a Iatchable, polarization-agile phase-shifter which is of high performance, low cost, small size and light weight and which is simple to construct.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

We claim:

1. A latchable, polarization-agile, microwave phase shifter assembly of the type including a first passive non-reciprocal quarter wave plate at a first terminal extremity thereof and a latching phase shifter axially adjacent to said first quarter wave plate, and comprising in combination:

a switchable non-reciprocal quarter wave plate axially adjacent said latching phase shifter,

a second passive non-reciprocal quarter wave plate axially adjacent said switchable quarter wave plate, and

a passive reciprocal quarter wave plate axially adjacent said second non-reciprocal quarter wave plate and forming a second terminal extremity of said phase shifter assembly.

2. The device of claim 1 in which said phase shifter is formed about a single ferrite longitudinal core and having said passive reciprocal quarter wave plate bonded to an axial extremity thereof.

3. The device of claim 1 in which said switchable non-reciprocal quarter wave plate comprises a ferrite yoke externally concentrically of a ferrite core of substantially rectangular cross section and having four equiangularly spaced radially extending pole pieces connecting said yoke and core in magnetic circuit, and

electromagnetic windings upon said pole pieces and interconnected in electrical circuit for oppositely magnetically exciting contiguous pole piece sectors of said yoke.

4. The device of claim 1 in which said phase shifter is formed about a single ferrite longitudinal core and having said passive reciprocal quarter wave plate bonded to an axial extremity of said core, and in which said switchable non-reciprocal quarter wave plate comprises I a ferrite yoke externally concentrically of a ferrite core of substantially rectangular cross section and having four equiangularly spaced radially extending pole pieces connecting said yoke and core in magnetic circuit, and

electromagnetic windings upon said pole pieces and interconnected in electrical circuit for oppositely magnetically exciting contiguous sectors of said yoke.

5. A polarization-agile, latchable, microwave phase shifter assembly of the type including a first and second passive non-reciprocal quarter wave plate at a respective first and second axial terminal extremity of a latching phase shifter and further comprising in combination therewith:

polarization switching means comprising a switchable non-reciprocal quarter wave plate axially interposed between said latching phase shifter and said second passive quarter wave plate for providing a selected one of three phase rotation states )\/4, M4 and O; and a passive reciprocal quarter wave plate axially adjacent said second passive non-reciprocal quarter wave plate and forming a terminal extremity of assembly is formed about a single ferrite longitudinal core and having said passive reciprocal quarter wave plate bonded to an axial extremity of said core.

7. The device of claim 5 in which said switchable non-reciprocal quarter wave plate comprises a ferrite yoke externally concentrically of a ferrite core of substantially rectangular cross section and having four equiangularly spaced radially extending pole pieces connecting said yoke and core in magnetic circuit and forming a first and second diametric pole pair, and

electromagnetic windings upon said pole pieces and inter-connected in electrical circuit for selectively magnetizing one of said pole pairs relative to the polarity of the magnetization of the other pole pair.

8. The device of claim 7 in which said ferrite yoke is comprised of four quadrant sections formed by two mutually orthogonal planes of symmetry each of which includes a longitudinal axis of said yoke and bisecting a mutually exclusive one of said pairs of diametrically opposed poles.

9. A polarization-agile, latchable, reciprocal phase shifter assembly comprising a first and second passive non-reciprocal quarter wave plate in axial magnetic circuit with latchable phase shift means and comprising respective first and second terminals of said phase shifter;

a switchable non-reciprocal quarter wave plate interposed in axial magnetic circuit between said phase-shift means and said second passive nonreciprocal quarter wave plate; and

a passive reciprocal quarter wave plate coupled to said second terminal for reciprocally providing an output having a selected one of a preselected linear polarization of a selected sense and a circular polarization in response to the application of an applied input of a preselected linear polarization and sense to said first input terminal and a selectible preselected state of said switchable nonreciprocal quarter wave plate.

l l =l= 

1. A latchable, polarization-agile, microwave phase shifter assembly of the type including a first passive non-reciprocal quarter wave plate at a first terminal extremity thereof and a latching phase shifter axially adjacent to said first quarter wave plate, and comprising in combination: a switchable non-reciprocal quarter wave plate axially adjacent said latching phase shifter, a second passive non-reciprocal quarter wave plate axially adjacent said switchable quarter wave plate, and a passive reciprocal quarter wave plate axially adjacent said second non-reciprocal quarter wave plate and forming a second terminal extremity of said phase shifter assembly.
 2. The device of claim 1 in which said phase shifter is formed about a single ferrite longitudinal core and having said passive reciprocal quarter wave platE bonded to an axial extremity thereof.
 3. The device of claim 1 in which said switchable non-reciprocal quarter wave plate comprises a ferrite yoke externally concentrically of a ferrite core of substantially rectangular cross section and having four equiangularly spaced radially extending pole pieces connecting said yoke and core in magnetic circuit, and electromagnetic windings upon said pole pieces and interconnected in electrical circuit for oppositely magnetically exciting contiguous pole piece sectors of said yoke.
 4. The device of claim 1 in which said phase shifter is formed about a single ferrite longitudinal core and having said passive reciprocal quarter wave plate bonded to an axial extremity of said core, and in which said switchable non-reciprocal quarter wave plate comprises a ferrite yoke externally concentrically of a ferrite core of substantially rectangular cross section and having four equiangularly spaced radially extending pole pieces connecting said yoke and core in magnetic circuit, and electromagnetic windings upon said pole pieces and interconnected in electrical circuit for oppositely magnetically exciting contiguous sectors of said yoke.
 5. A polarization-agile, latchable, microwave phase shifter assembly of the type including a first and second passive non-reciprocal quarter wave plate at a respective first and second axial terminal extremity of a latching phase shifter and further comprising in combination therewith: polarization switching means comprising a switchable non-reciprocal quarter wave plate axially interposed between said latching phase shifter and said second passive quarter wave plate for providing a selected one of three phase rotation states - lambda /4, lambda /4 and 0; and a passive reciprocal quarter wave plate axially adjacent said second passive non-reciprocal quarter wave plate and forming a terminal extremity of said assembly.
 6. The device of claim 5 in which said phase shifter assembly is formed about a single ferrite longitudinal core and having said passive reciprocal quarter wave plate bonded to an axial extremity of said core.
 7. The device of claim 5 in which said switchable non-reciprocal quarter wave plate comprises a ferrite yoke externally concentrically of a ferrite core of substantially rectangular cross section and having four equiangularly spaced radially extending pole pieces connecting said yoke and core in magnetic circuit and forming a first and second diametric pole pair, and electromagnetic windings upon said pole pieces and inter-connected in electrical circuit for selectively magnetizing one of said pole pairs relative to the polarity of the magnetization of the other pole pair.
 8. The device of claim 7 in which said ferrite yoke is comprised of four quadrant sections formed by two mutually orthogonal planes of symmetry each of which includes a longitudinal axis of said yoke and bisecting a mutually exclusive one of said pairs of diametrically opposed poles.
 9. A polarization-agile, latchable, reciprocal phase shifter assembly comprising a first and second passive non-reciprocal quarter wave plate in axial magnetic circuit with latchable phase shift means and comprising respective first and second terminals of said phase shifter; a switchable non-reciprocal quarter wave plate interposed in axial magnetic circuit between said phase-shift means and said second passive non-reciprocal quarter wave plate; and a passive reciprocal quarter wave plate coupled to said second terminal for reciprocally providing an output having a selected one of a preselected linear polarization of a selected sense and a circular polarization in response to the application of an applied input of a preselected linear polarization and sense to said first input terminal and a selectible preselected state of said switchable non-reciprocal quarter wave plate. 